Polyguaiacol: a useful model polymer for lignin biodegradation research

Abstract

A polymer of ring-labeled [C]o-methoxyphenol ([C]guaiacol) was prepared by peroxidase-H(2)O(2)-catalyzed oxidation of the C-labeled monomeric compound. The ring-labeled [C]polyguaiacol contained 67.71% carbon, 5.09% hydrogen, 27.49% oxygen, 25.44% methoxyl, and 8.60% phenolic hydroxyl. The polymer had an average molecular weight of between 5,000 and 15,000, as determined by gel chromatography. A schematic representation of the polymer, similar to previously published structures of polyguaiacols, was devised to meet these and other analytical parameters. The polymer is primarily composed of o-o and p-p-linked guaiacol moieties, with an occasional o-p-biphenyl link and some p-diphenoquinone structures. An approximate molecular formula is [C(49)O(14)H(31)](n), where n =/> 5.8. Its C(6) formula is C(6)H(2.3)O(0.3) (OH)(0.7)(OCH(3))(1.0). Polyguaiacol has many of the characteristics of a synthetic lignin. It is easier and less expensive to prepare than standard synthetic lignins (dehydrogenation polymers of coniferyl alcohol). It is degraded ([C]polyguaiacol --> CO(2)) by the lignolytic system of the white-rot fungus Phanaerochaete chrysosporium. It is suggested that [C]polyguaiacol may be of value as a substrate for lignin biodegradation research.